Shadow regions detection algorithm by adaptive narrowband two-phase Chan-Vese model

An adaptive narrowband two-phase Chan-Vese （ANBCV） model is proposed for improving the shadow regions detection performance of sonar images. In the first noise smoothing step, the anisotropic second-order neighborhood MRF （Markov Random Field, MRF） is used to describe the image texture feature parameters. Then, initial two-class segmentation is processed with the block mode k-means clustering algorithm, to estimate the approximate position of the shadow regions. On this basis, the zero level set function is adaptively initialized by the approximate position of shadow regions. ANBCV model is provided to complete local optimization for eliminating the image global interference and obtaining more accurate results. Experimental results show that the new algorithm can efficiently remove partial noise, increase detection speed and accuracy, and with less human intervention.

Experimental Observation of the Ore-Forming Fluid NaCl-H_2O System in the Earth Interior

The NaCl-H_2O binary system is a major component of solutions coexisting with ores. Observation ofsaturated solutions of NaCl-H_2O by using the method of hydrothermal diamond anvil cell (HDAC) is a new approach tothe study of ore-forming fluids. The salinities of NaCl-H_2O solutions in experimental observation are in a range of 32-55%. The observed temperature range is 25℃-850℃, and the pressure range 1 atm-10 kb. In this temperature-pressure range, the supercritical single phase, two phases (L,V) close to the critical state and two-phased (L+V) immis-cible region were observed. And for the salinity of 35% the two phase L+V immiscible region of NaCl-H_2O solutionwas observed in a range of 253-720℃. Another temperature range, 400-817℃, was observed for the immiscible two-phased region of 50% salinity solution. In the high-temperature part of the two-phased immiscible region, the phase na-ture is very unstable. A "critical phenomenon" was observed when the heating path was very close to the critical state.It is possible to observe a 'critical phenomenon': an "explosion" occurred almost constantly at the interface between theliquid and vapour and the interface is rather obscure. A continuous transition between phases L and V could be foundin the immiscible L+V phase while heating continuously. Moreover, as the NaCl-H_2O solution was separated into liq-uid and vapour phases, static charges surrounding each vapour bubble could be seen, and these bubbles were attractedtogether by the static charges to form a special solution structure. Besides, critical states of different salinities of NaCl-H_2O were observed in order to study the properties of the fluids occurring in the rocks in the earth interior, the origin ofore-bearing fluids and the significance of supercritical fluid with respect to the ore formation. The comparison of the sa-linity data of the fluid inclusions in the minerals of ore deposits with observations of NaCl-H_2O under HDAC in theconditions of high temperatures and pressures, combined with further thermodynamic analysis of ore-formation condi-tions would explain in depth the factors determining the ore formation.

Thermal and mechanical characteristics of a thermal pile in permafrost regions

Cast-in-place pile foundations are widely used in permafrost regions to support buildings.The stability of cast-in-place pile foundations is highly sensitive to permafrost thermal regime changes.Permafrost degradation caused by climate change is increasing the disaster risk of castin-place pile foundations.However,proactive cooling methods for cast-in-place pile foundations are seldom reported.The cold energy produced by two-phase closed thermosyphons(TPCTs)can efficiently prevent the permafrost thermal regime from being disturbed by engineering activities and climate change.TPCTs were installed in a concrete pile forming a thermal pile.Then,a model experiment was conducted to explore the thermal regime,influence scope,dissipation process of cold energy,and freezing strength of the thermal pile.The results indicated that the thermal pile may significantly cool the foundation soil.Most of cold energy produced by the thermal pile dissipated during the warm period,and the cooling scope of the thermal pile can cover the area within a 40 cm(twice the pile diameter)radius around the pile.Additionally,the TPCTs can significantly improve freezing strength between the thermal pile and frozen soil.The lesson learned from this study can provide a new approach to control the thermal regime of cast-in-place pile foundation in permafrost,which was of valuable to the construction of pile foundations in cold regions.

用3D-CAFE法分析430铁素体不锈钢凝固过程中的温度场

用3D-CAFE模拟计算得到凝固组织与试验基本一致,采用3D-CAFE法对空冷条件下430铁素体不锈钢凝固过程的温度场进行了分析,在凝固过程中,相同位置不同时刻的温差呈减小趋势,相同时刻不同位置的温差也减小,液相中温度梯度降低,固液两相区内温度不断降低,固液两相区内的温度梯度呈增加趋势;不同时刻,从表面到中心固液两相区内的温度梯度降低。